/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * net/utils/net_ipv6_pref2mask.c
 *
 *   Copyright (C) 2015 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <tinyara/net/ip.h>

#include "utils/utils.h"

#ifdef CONFIG_NET_IPv6

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Function: net_ipv6_pref2mask
 *
 * Description:
 *   Convert a IPv6 prefix length to a network mask.  The prefix length
 *   specifies the number of MS bits under mask (0-128)
 *
 * Parameters:
 *   preflen  - Determines the width of the netmask (in bits).  Range 0-128
 *   mask  - The location to return the netmask.
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void net_ipv6_pref2mask(uint8_t preflen, net_ipv6addr_t mask)
{
	unsigned int bit;
	unsigned int i;

	/* Set the network mask.  preflen is the number of MS bits under the mask.
	 *
	 * Eg. preflen = 38
	 *     NETMASK: ffff ffff fc00 0000  0000 0000 0000 0000
	 *     bit:                                       1 1..1
	 *                 1 1..3 3..4 4..6  6..7 8..9 9..1 1..2
	 *              0..5 6..1 2..7 8..3  4..9 0..5 6..1 2..7
	 *     preflen:                                   1 1..1
	 *                 1 1..3 3..4 4..6  6..8 8..9 9..1 1..2
	 *              1..6 7..2 3..8 9..4  5..0 1..6 7..2 3..8
	 */

	for (i = 0; i < 7; i++) {
		/* bit = {0, 16, 32, 48, 64, 80, 96, 112} */

		bit = i << 4;

		if (preflen > bit) {
			/* Eg. preflen = 38, bit = {0, 16, 32} */

			if (preflen > (bit + 16)) {
				/* Eg. preflen = 38, bit = {0, 16} */

				mask[i] = 0xffff;
			} else {
				/* Eg. preflen = 38, bit = {32}
				 *     bit - preflen = 6
				 *     make = 0xffff << (16-6)
				 *          = 0xfc00
				 */

				mask[i] = 0xffff << (16 - (bit - preflen));
			}
		} else {
			/* Eg. preflen=38, bit= {48, 64, 80, 112} */

			mask[i] = 0x0000;
		}
	}
}

#endif							/* CONFIG_NET_IPv6 */
